Using a semi-intact, behaving preparation of a marine crustacean, Semibalanus cariosus, the objective of the proposed research is to study three interacting and well-defined motor systems by simultaneous intracellular recording from identified motor neurons and the local circuit interneurons that control them: a) Each of the impaled neurons will be injected with CoCl2, subsequently precipitated as CoS and intensified with silver. This will reveal the details of the structure of the dendritic arborizations in the neuropile. b) Connections between neurons will be detected by passing current through the impaling electrodes, by sensory input, and by antidromic stimulation of motor neurons. c) Behavioral of the systems will be monitored by observation, by intra- and extracellular recording of muscle junction potentials, and by measurement of tension of affected muscles. d) These techniques will give information on the morphology, electrical activity, connectivity, mode of transmission, and effect on motor output of a little-known class of neurons that comprises the most numerous type found in the nervous systems of all higher animals.